Numerous attempts have been made at creating an accurate, reliable, and affordable tire-pressure monitoring system. It seems that Pirelli has finally cracked the code with the K-Pressure Optic. Replacing the regular cap on the valve stem, the K-Pressure shows white if the tire pressure is good, then turns red if it sinks below the nominal level by about 12 percent. The translucent plastic gizmo is the tool used to remove a K-Pressure. Do we really need things like this? As speeds go up and sidewall heights go down, yes, a lot of us do.
Tire pressures for highway use has been a hotly debated issue ever since the Ford Explorer fiasco. Manufacturers of tires and vehicles have been arguing about how to best go about a warning system that alerts a driver when a tire has lost enough air to warrant an alert. With the government also involved, the process became more complex yet. As it stands, every newly registered car from September 2007 and on must have a tire-pressure monitoring system. For example, many Grand Cherokees already do, and Chrysler now has to deal with "false alarms" just from differences in ambient temperature. Somewhat complicated and costly, tire-pressure monitoring systems are unfortunately here to stay, at least until common sense gets back in vogue again. Meanwhile, Pirelli developed an affordable and deceivingly simple series of tire-pressure monitors that aren't even vehicle- or wheel-specific.
Replacing the regular cap on a valve stem, the K-Pressure doesn't require any wiring, doesn't affect tire mounting, and is affordable. Also, at 3.5 grams, it really doesn't affect balance. Currently available in 12 different pressure settings from 26 to 44 psi and sold in pairs-since front and rear tires usually require different pressures-the Pirelli monitors can be used on most vehicles.
It doesn't get any easier: If the cap shows white, you're good to go, and if it shows red, you need to add air and/or find the source of the leak. Normally, a tire loses about one psi per month from permeation (the air molecules actually migrate through the tire) and a glance at the K-pressure will tell when it's time to replenish the tire.
One problem facing the K-Pressure Optic is its simple appearance, which will cause many to confuse it with the cheap parts-store versions. Frankly, when we first saw the K-Pressures, we didn't think much of them either. But after learning that they are both temperature- and altitude-compensating, and unlike the (supposedly now recalled) cheapies cannot cause air loss, we looked at these little marvels in a whole different way.
While the K-pressure Optic is mechanical, in the near future Pirelli will also offer the K-Pressure Acoustic and AcousticBlue. The former is capable of communicating with a vehicle's onboard electronic management system while the 'Blue version uses Bluetooth-enabled cell phones to relay its data. This is done with a microprocessor inside the K-Pressure, powered by a battery with a 5,000-hour service life. That may not sound like a long time, but since they go idle when the vehicle isn't driven, it translates into many years of use.
Why not just check the tire pressure with a gauge every now and then? Well, other than for trail use, most of us rarely do. Wouldn't it be convenient to just peek at four K-Pressures instead of actually taking a gauge to each tire? Yes, it sure would save some wear and tear on the knees, and time. Plus, every time you use a tire gauge, you also let a little air out and disturb the valve core, which in itself can start a leak. That's one reason truckers favor clubs over gauges.
So what are the drawbacks? As far as we can tell, there are only three potential reasons not to use K-Pressure Optic tire monitors. If you use them on a trail-driven vehicle, you'll probably get tired of the theft-resistant feature pretty quickly (a special included tool is needed to remove them), so they're better off being on something you don't normally air down. Also, since the K-pressure is about twice as long as a regular cap, it can end up outside the rim, or even the tire, on some wheels. Similarly, a rubber valve stem by itself does bend from centrifugal force at speed if it's at an outward angle on the rim, and adding the weight of the K-Pressure doesn't help. The latter two can be circumvented by using metal valve stems, angled or straight as needed. However, the K-Pressure is approved by the very strict TUV (the German version of DOT) on rubber valve stems too.
Selling for about $60 a set, a cost that Pirelli feels will be paid back within a year on fuel savings and tire wear alone, the K-pressure can be a good investment for the daily driver and the tow vehicle.